What is Rolling Friction?
For a solid body in motion, there are two foremost kinds of friction that execute at a given time.
The force which opposes the rolling action of a moving body on a plane is depicted as rolling friction or rolling resistance.
The examples of rolling friction are given by rolling of a football or motion of a truck wheel on the ground.
The supplementary kind of friction is also known as sliding friction. In this category of friction, there is a limit on the movement of the body as one of its sides is in contact with the surface.
An example of sliding friction can be illustrated as pushing a box across the table.
Rolling friction is significantly powerless than sliding friction. The picture given below is showing sliding and rolling friction respectively.
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Rolling Friction Examples
When an object is moved upon a surface, certain effects occur:
The body is distorted at the contact point with the plane.
The surface is mutilated at the contact point with the body.
Movement is created underneath the superficial consequently.
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The main cause of this friction is that the energy of distortion is greater than the energy of retrieval. Also, there is a bonding force between the two plains which requires being overwhelmed continuously. The quantity of friction is built on numerous factors such as:
The eminence of the surface
The superiority of the sliding object
Weight (mass)
The rolling object’s diameter
The object’s Surface area
Below is some unremarkable example for rolling friction
A car will ultimately come to discontinue its motion if only permitted to move as the friction between the wheels and the road surface originates from friction that helps the vehicle to stop.
Thicker bike wheels will decrease the bike’s potential speed because there is a better wheel surface to generate friction alongside the surface to decelerate the bike.
Heavy-duty trucks get superior gas range when tread initiates to grab on the tires. This is because there is a chance of a smaller amount of rolling friction,that lets the truck transfer more rapidly with less resistance.
On a slight failure, a skateboard set will halt by itself ultimately on account of the resistance produced by the friction between the exterior and the wheels.
A football hit out across a grassy ground will crawl down faster than the one-hit out across an even, firm surface as the rolling friction is far superior on the field.
While a train travels around a bend there is superior rolling friction.
Roller skates have superior rolling friction as compared to the Rollerblades as there is additional touching base between surface and wheel on roller skates.
Rolling friction in a duckpin bowling ball is probable to have less than a full-size bowling ball as less rolling friction is created based upon its weight and size.
More rolling friction will be obligated to a dump truck rather than a small car since the truck is a weightier load pressuring on the wheel and consequently initiating superior rolling friction.
As we can understand, numerous things practice rolling friction every day. There are illustrations all over the world.
Rolling Friction Formula
The rolling friction comprises of three laws, that are:
The force of rolling friction declines with the rise in softness.
Rolling friction is stated as the multiplication of load and the fractional power constant.
F = k * Ln
Rolling friction force is inversely proportional to the radius of curvature as well as directly proportional to load.
F = μ × \[\frac{w}{r}\]
Calculating the coefficient of the friction is significantly more composite as compared to sliding friction.
The coefficient of rolling friction is shown as the fraction of the force of rolling friction to the total weight of the object.
In experiential expressions, the coefficient of rolling resistance can be stated as:
Fr = μr * W
Here,
Fr = rolling resistance resistivity
W = rolling body’s weight of the
μr = coefficient of rolling resistance
Rolling friction and rolling resistance
The force that repels the movement of a body progressing on a certain surface is known as the rolling friction or the rolling resistance.
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The rolling resistance can be shown as
Fr = c * W
Where,
Fr = rolling friction or rolling resistance (N)
c = rolling resistance coefficient. It is dimensionless (CRF - coefficient of rolling friction)
Again we know that
W = m * ag
Where,
W = usual force, or weight of the body (N)
m = mass of body (kg)
ag = acceleration due to gravity (9.81 m/s2)
Further, the rolling resistance can be stated as;
Fr = cl W/r
Here,
cl = rolling resistance coefficient and its dimension in length (mm) alternatively known as the coefficient of rolling friction.
W = natural force, or the weight of the body in N
r = the wheel’s radius in mm
FAQs on Rolling Friction and Rolling Resistance
1. What is rolling friction as per the Class 11 Physics syllabus?
Rolling friction is the resistive force that opposes the motion when an object, such as a wheel, ball, or cylinder, rolls over a surface. This force arises primarily from the non-elastic deformation of the object and the surface at the point of contact. As the object rolls, the surface it presses down on deforms slightly, and the object has to continuously climb out of this small depression, creating resistance.
2. What is the main difference between rolling friction and sliding friction?
The main difference lies in their magnitude and cause. Rolling friction is significantly weaker than sliding (kinetic) friction for the same objects. This is because rolling involves deformation of surfaces, while sliding involves the breaking of microscopic bonds and irregularities rubbing against each other. This is why it's much easier to move heavy objects using wheeled carts rather than dragging them.
3. What is the formula used to calculate the force of rolling friction?
The formula to calculate the force of rolling friction (Fᵣ) is given by:
Fᵣ = μᵣ * N
Where:
- Fᵣ is the force of rolling friction.
- μᵣ (mu-r) is the coefficient of rolling friction, which is a value that depends on the materials of the rolling object and the surface.
- N is the normal force, which is the force exerted by the surface on the object, perpendicular to the surface. For an object on a horizontal surface, N is equal to its weight (mg).
4. What are the key factors that affect rolling resistance?
Several factors influence the magnitude of rolling resistance. The most important ones include:
- The Normal Force (N): A heavier object will exert a greater normal force, leading to more deformation and higher rolling resistance.
- The Radius of the Rolling Object: Larger wheels or rollers generally experience less rolling resistance for a given load.
- Material Properties: The hardness and elasticity of both the wheel and the surface are crucial. Softer, more deformable materials (like a flat tire) increase rolling resistance.
- Surface Condition: A rough or soft surface (like sand or mud) causes much more resistance than a smooth, hard surface (like concrete).
5. Why does rolling friction occur at all, especially between two very hard and smooth objects like a steel ball on a steel plate?
Even the hardest and smoothest objects are not perfectly rigid. At a microscopic level, when the ball presses on the plate, it causes a tiny amount of deformation in both surfaces. As the ball rolls forward, the material in front of it is compressed, and the material behind it expands back. This compression-expansion cycle is not perfectly elastic; some energy is lost as heat, a phenomenon known as hysteresis. This energy loss manifests as the resistive force we call rolling friction.
6. In physics, is there a difference between the terms 'rolling friction' and 'rolling resistance'?
For the scope of the CBSE Class 11 syllabus, the terms rolling friction and rolling resistance are often used interchangeably to refer to the force opposing a rolling object's motion. However, in more advanced engineering contexts, 'rolling resistance' can be a broader term that includes rolling friction as its main component, along with other factors like bearing friction and air drag. For exam purposes, you can consider them to mean the same thing: the resistive force due to surface deformation.
7. Why is it significantly easier to pull a suitcase with wheels than to drag the same suitcase without wheels?
This is a direct application of the principles of friction. When you drag the suitcase, you are working against sliding friction, which is relatively high. When you pull the suitcase on its wheels, you are working against rolling friction. The coefficient of rolling friction is typically 100 to 1000 times smaller than the coefficient of sliding friction. Therefore, the force required to overcome rolling friction is much less, making it significantly easier to move the suitcase.
8. Does the speed of a rolling object affect the force of rolling resistance?
At the speeds typically considered in high school physics problems, the force of rolling resistance is considered to be nearly independent of speed. Unlike air resistance, which increases dramatically with speed, rolling resistance remains relatively constant. Therefore, for most calculations as per the NCERT syllabus for the 2025-26 session, you can assume that speed does not change the value of rolling friction.
